Slot cooling fins in electrical machines

ABSTRACT

A method for manufacturing a stator for an electric machine comprises manufacturing a slot cooling fin to extend into a slot defined between a first tooth, a second tooth, and a stator yoke, and disposing a coil in the slot, wherein the slot cooling fin extends into the first coil.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of, and claims priority to, and thebenefit of U.S. patent application Ser. No. 16/922,808, filed on Jul. 7,2020, and entitled “SLOT COOLING FINS IN ELECTRICAL MACHINES.” The '808application is a divisional of, and claims priority to, and the benefitof U.S. patent application Ser. No. 15/875,550, filed on Jan. 19, 2018,and entitled “SLOT COOLING FINS IN ELECTRICAL MACHINES,” which issued onAug. 11, 2020, as U.S. Pat. No. 10,742,098. All of which areincorporated by reference herein in their entirety for all purposes.

FIELD

The present disclosure relates to electric motors or electricgenerators, and more specifically, to a system for cooling an electricmotor or electric generator.

BACKGROUND

Electrical machine stators consist of slots and teeth, with conductivecoils (copper or aluminum) placed in the stator slots. When current ispassed through the coils, the coils generate heat and hot spots aretypically present in the middle of the coils.

SUMMARY

In various embodiments, the present disclosure provides a method ofmanufacturing a stator for an electric machine. The method may comprisemanufacturing a slot cooling fin to extend into a slot defined between afirst tooth, a second tooth, and a stator yoke, and disposing a coil inthe slot, wherein the slot cooling fin extends into the first coil.

In various embodiments, the coil surrounds the slot cooling fin.

In various embodiments, the slot cooling fin extends from at least oneof the stator yoke or the first tooth.

A planar member for a stator stack is disclosed herein, comprising astator yoke defining a central longitudinal axis, a first surface facingradially outward, and a second surface facing radially inward, a toothextending radially inwards from the second surface, a first tooth tipextending circumferentially from a radially inward end of the tooth, asecond tooth tip extending circumferentially from the radially inwardend of the tooth; a first slot portion defined between the first toothtip and the second surface, a second slot portion defined between thesecond tooth tip and the second surface, and a slot cooling finextending radially from the stator yoke into the first slot portion.

In various embodiments, the stator yoke, the tooth, the first tooth tip,the second tooth tip, and the slot cooling fin extend within a planeoriented orthogonal to the central longitudinal axis.

In various embodiments, the slot cooling fin comprises a cantilever.

In various embodiments, the slot cooling fin is disposed radiallybetween the stator yoke and the first tooth tip.

In various embodiments, the first tooth tip extends circumferentiallyfrom a radially inward end of the tooth, the second tooth tip extendscircumferentially from the radially inward end of the tooth, and thefirst tooth tip and the second tooth tip extend in opposite directionsfrom the tooth.

In various embodiments, the slot cooling fin is configured to extendinto a coil.

In various embodiments, a first end of the slot cooling fin is coupledto the stator yoke and a second end of the slot cooling fin extends intothe first slot portion in a cantilevered manner.

An electric machine is disclosed herein, comprising a rotor and astator. The stator comprises a stator yoke defining a centrallongitudinal axis, a first surface facing radially outward, and a secondsurface facing radially inward, a first tooth extending radially inwardsfrom the second surface, a first tooth tip extending circumferentiallyfrom a radially inward end of the first tooth, a second tooth tipextending circumferentially from the radially inward end of the firsttooth, a second tooth extending radially inwards from the secondsurface, a third tooth tip extending circumferentially from a radiallyinward end of the second tooth, a fourth tooth tip extendingcircumferentially from the radially inward end of the second tooth, aslot disposed between the first tooth and the second tooth, and a slotcooling fin. The slot comprises a first slot portion defined between thefirst tooth tip and the second surface, and a second slot portiondefined between the third tooth tip and the second surface, wherein theslot cooling fin extends radially from the stator yoke into the firstslot portion.

In various embodiments, the electric machine further comprises a coildisposed in the slot.

In various embodiments, the slot cooling fin extends into the coil.

In various embodiments, the coil surrounds the slot cooling fin.

In various embodiments, the first tooth tip and the second tooth tipextend in opposite directions from the tooth.

In various embodiments, the stator yoke, the first tooth, the firsttooth tip, the second tooth tip, and the slot cooling fin extend withina plane oriented orthogonal to the central longitudinal axis.

In various embodiments, the slot cooling fin comprises a cantilever.

In various embodiments, the slot cooling fin is disposed radiallybetween the stator yoke and the first tooth tip.

In various embodiments, the slot cooling fin is configured to cool thecoil.

In various embodiments, the slot cooling fin provides a thermal pathfrom an inner portion of the coil to the stator yoke.

The foregoing features and elements may be combined in variouscombinations without exclusivity, unless expressly indicated hereinotherwise. These features and elements as well as the operation of thedisclosed embodiments will become more apparent in light of thefollowing description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an electric machine, such as an electricmotor or an electric generator, in accordance with various embodiments;

FIG. 2A is a perspective view of a slot defined in a stator stack, inaccordance with various embodiments;

FIG. 2B is an end view of a planar member for a stator stack, inaccordance with various embodiments;

FIG. 3A is a cross-section view a stator stack having a plurality ofslot cooling fins extending circumferentially into stator coils, inaccordance with various embodiments;

FIG. 3B is a slot cooling fin having a keyhole geometry, in accordancewith various embodiments;

FIG. 3C is a slot cooling fin having a tapered geometry, in accordancewith various embodiments;

FIG. 4 is a cross-section view a stator stack having a plurality of slotcooling fins extending radially into stator coils, in accordance withvarious embodiments;

FIG. 5 is a schematic flow chart diagram of a method of manufacturing astator for an electric machine, in accordance with various embodiments;

FIG. 6A is a schematic view of a double-layer concentrated windingarchitecture, in accordance with various embodiments;

FIG. 6B is a schematic view of a single-layer concentrated windingarchitecture, in accordance with various embodiments; and

FIG. 6C is a schematic view of a distributed winding architecture, inaccordance with various embodiments, in accordance with variousembodiments.

The subject matter of the present disclosure is particularly pointed outand distinctly claimed in the concluding portion of the specification. Amore complete understanding of the present disclosure, however, may bestbe obtained by referring to the detailed description and claims whenconsidered in connection with the drawing figures, wherein like numeralsdenote like elements.

DETAILED DESCRIPTION

The detailed description of exemplary embodiments herein makes referenceto the accompanying drawings, which show exemplary embodiments by way ofillustration. While these exemplary embodiments are described insufficient detail to enable those skilled in the art to practice thedisclosure, it should be understood that other embodiments may berealized and that logical changes and adaptations in design andconstruction may be made in accordance with this disclosure and theteachings herein without departing from the spirit and scope of thedisclosure. Thus, the detailed description herein is presented forpurposes of illustration only and not of limitation.

A stator of the present disclosure may aid in efficiently removing heatfrom stator coils (typically for concentrated winding machines, wherethere are less slots and more slot area). A stator of the presentdisclosure may aid in improving leakage inductance by providing a pathfor leakage flux and reducing short circuit current. Efficient heatremoval from the middle of the stator slots may allow for the stator ofthe present disclosure to be suitable for operating at a higher currentdensity, increased power density, increased leakage inductance, and lowshort circuit current.

In various embodiments, and with reference to FIG. 1 , an electricmachine 100, such as an electric motor or an electric generator, havinga plurality of slot cooling fins is disclosed herein. An XYZ axes isprovided for ease of illustration. The electric machine 100 generallyincludes a stator 105 and a rotor 110. In various embodiments, theelectric machine 100 is an electric motor or an electric generator of anaircraft.

As used herein, the terms axial, radial, and circumferential arerelative to the central longitudinal axis 115 of the stator 105. Thatis, a first component that is “radially outward” of a second componentmeans that the first component is positioned at a greater distance awayfrom the central longitudinal axis 115 of the stator 105 than the secondcomponent. Correspondingly, a first component that is “radially inward”of a second component means that the first component is positionedcloser to axis 115 than the second component. Accordingly, in the caseof the stator 105, components that are radially inward of othercomponents and that rotate circumferentially about the centrallongitudinal axis 115 rotates through a circumferentially shorter paththan the other components. Similarly, the term “axial” generally refersto a position along the central longitudinal axis 115. As used herein,“distal” refers to the direction outward, or generally, away fromcentral longitudinal axis 115. As used herein, “proximal” refers to adirection inward, or generally, towards central longitudinal axis 115.

In various embodiments, with reference to FIG. 1 , electric machine 100includes an external housing 150. Stator 105 may be disposed withinexternal housing 150. A plurality of external cooling fins 155 mayextend from external housing 150. External cooling fins 155 may coolexternal housing 150. External housing 150 may comprise a metalmaterial. External cooling fins 155 may comprise a metal material. Invarious embodiments, external housing 150 and external cooling fins 155may be manufactured as a single piece.

With reference to FIG. 2A, an isolated view of a plurality of separateplanar members 116 of the stator, also referred to herein as “statorstack” 105 is illustrated, in accordance with various embodiments.Stator stack 105 may comprise central longitudinal axis 115. Statorstack 105 may include a plurality of separate planar members 116 thatare held together by a binder or an adhesive. Planar members 116 maycomprise silicon steel. Stator stack 105 may have a first axial end 111and a second axial end 112 opposite the first axial end 111.

With reference to FIG. 2B, an axial view of a planar member 116 isillustrated, in accordance with various embodiments. In variousembodiments, planar member 116 may comprise a stator yoke 260 comprisinga central longitudinal axis 215, a first axial surface 281, a secondaxial surface 282 opposite the first axial surface 281, a first surface284 facing radially outward, and a second surface 285 facing radiallyinward. Planar member 116 may comprise a plurality of teeth extendingradially inwards from second surface 285. For example, a tooth (alsoreferred to herein as a first tooth) 261 and a tooth (also referred toherein as a second tooth) 262 may extend from second surface 285. Twotooth tips may extend circumferentially from a proximal end of eachtooth. Stated differently, two tooth tips may extend circumferentiallyfrom a radially inward end of each tooth. For example, tooth tip (alsoreferred to herein as a first tooth tip) 263 and tooth tip (alsoreferred to herein as a second tooth tip) 264 may extend from proximalend (also referred to herein as a radially inward end) 268 of tooth 261.Tooth tip 263 may extend in an opposite direction from tooth 261 astooth tip 264. In this regard, tooth 261, tooth tip 263, and tooth tip264 may form a substantially T-shaped member. Similarly, tooth tip (alsoreferred to herein as a third tooth tip) 265 and tooth tip (alsoreferred to herein as a fourth tooth tip) 266 may extend from proximalend (also referred to herein as a radially inward end) 269 of tooth 262.

In various embodiments, a slot 270 may be formed between tooth 261 andtooth 262. Slot 270 may comprise a first slot portion 271 definedbetween the tooth tip 264 and stator yoke 260. First slot portion 271may be defined between tooth tip 264 and second surface 285. Slot 270may comprise a second slot portion 272 defined between the tooth tip 265and stator yoke 260.

In various embodiments, a slot cooling fin may extend into a slot. Forexample, a cooling fin 251 may extend from tooth 261. A slot cooling fin252 may extend from tooth 261. Slot cooling fin 252 may extend intofirst slot portion 271. Slot cooling fin 252 may extend in thecircumferential direction from tooth 261. A slot cooling fin 253 mayextend from tooth 262 into second slot portion 272. A slot cooling fin254 may extend from tooth 262 in an opposite direction from slot coolingfin 253.

Although illustrated as extending from tooth 261 at substantiallyhalfway between stator yoke 260 and tooth tip 264, it is contemplatedherein that, in various embodiments, slot cooling fin 252 may extendfrom tooth 261 at any radial location between stator yoke 260 and toothtip 264. The radial location may be chosen depending on the desiredlocation for cooling.

With reference to FIG. 3A, a cross-section view of electric machine 100is illustrated, in accordance with various embodiments. With combinedreference to FIG. 2B, and FIG. 3A, stator 105 may include stator coils350. Stator coils 350 may comprise a plurality of electricallyconductive wires. In various embodiments, stator coils 350 may comprisecopper, copper alloy, aluminum, aluminum alloys, nickel, nickel basedalloys, titanium-based materials, or electrically conductive carbonmaterials, among others. Stator coils 350 may include a coil (alsoreferred to herein as a first coil) 351 surrounding tooth 261 and a coil(also referred to herein as a second coil) 352 surrounding tooth 262. Inthis regard, both coil 351 and coil 352 may be at least partiallydisposed in slot 270.

In various embodiments, slot cooling fin 252 may extend into coil 351.Stated differently, coil 351 may surround slot cooling fin 252. Duringoperation, slot cooling fin 252 may cool coil 351. Slot cooling fin 252may provide a thermal path 290 for heat to travel from coil 351 toexternal cooling fins 155. Forming slot cooling fin 252 within coil 351may aid in preventing localized hot spots within stator 105, as mayotherwise occur if conventional techniques were employed without a slotcooling fin, according to various embodiments. Slot cooling fin 252 maycomprise a cantilever. Stated differently, slot cooling fin 252 may besupported at only one end. Planar member 116 may extend within a planeoriented orthogonal to central longitudinal axis 215. Centrallongitudinal axis 215 may be concentric with central longitudinal axis115, with momentary reference to FIG. 1 .

With reference to FIG. 3B, a slot cooling fin 301 is illustrated, inaccordance with various embodiments. Slot cooling fin 252 of FIG. 3A maybe similar to slot cooling fin 301, in various embodiments. Slot coolingfin 301 may comprise a “keyhole” geometry. Stated differently, slotcooling fin 301 may comprise a swollen end 305. Slot cooling fin 301 maybe coupled to planar member 116 at end 304, with momentary reference toFIG. 3A.

With reference to FIG. 3C, a slot cooling fin 302 is illustrated, inaccordance with various embodiments. Slot cooling fin 252 of FIG. 3A maybe similar to slot cooling fin 302, in various embodiments. Slot coolingfin 302 may comprise a tapered geometry. Stated differently, slotcooling fin 302 may be tapered from end 306 towards end 307. Slotcooling fin 301 may be coupled to planar member 116 at end 306, withmomentary reference to FIG. 3A.

In various embodiments, with reference to FIG. 4 , it is contemplatedherein that a slot cooling fin 452 may extend radially inwards fromsecond surface 285 of stator yoke 260. Slot cooling fin 452 may extendfrom second surface 285 at a location from tooth 261 which is at leastone of less than or greater than a midpoint 495 between tooth 261 andtooth 262. Stated differently, slot cooling fin 452 may not be a dividerbetween coil side 351 and coil side 352, but rather may extend into aninner portion of coil side 351. In various embodiments, slot cooling fin454 may be circumferentially aligned with tooth tip 264.

With reference to FIG. 5 , a method 500 for manufacturing a stator of anelectric machine is illustrated, in accordance with various embodiments.Method 500 includes manufacturing a slot cooling fin to extend into aslot defined between a first tooth, a second tooth, and a stator yoke(step 510). Method 500 includes disposing a first coil to surround thefirst tooth (step 520). Method 500 includes disposing a second coil tosurround the second tooth (step 530).

With combined reference to FIG. 2B, FIG. 3A and FIG. 5 , step 510 mayinclude manufacturing slot cooling fin 252 to extend into slot 270defined between first tooth 261, second tooth 262, and stator yoke 260.Step 510 may include additive manufacturing, subtractive manufacturing,or any other suitable manufacturing methods. Step 520 may includedisposing first coil 351 to surround the first tooth 261. Slot coolingfin 252 may extend into first coil 351 in response to first coil 351being wrapped around first tooth 261. Step 520 may include wrappingfirst coil 351 around first tooth 261. Step 530 may include disposingsecond coil 352 to surround second tooth 262. Step 530 may includewrapping second coil 352 around second tooth 262.

With regards to FIG. 6A, a schematic view of a double-layer concentratedwinding architecture 601 with planar members 116 is illustrated, inaccordance with various embodiments. Double-layer concentrated windingarchitecture 601 may be similar to the winding architecture asillustrated in FIG. 4 . In this regard, each slot of planar member 116may include two separate windings (also referred to herein as coils).

With regards to FIG. 6B, a schematic view of a single-layer concentratedwinding architecture 602 with planar members 116 is illustrated, inaccordance with various embodiments. In this regard, each slot of planarmember 116 may include a single winding (also referred to herein ascoil).

With regards to FIG. 6C, a schematic view of a distributed windingarchitecture 603 with planar members 116 is illustrated, in accordancewith various embodiments. In this regard, each slot of planar member 116may include a single winding (also referred to herein as coil).

In this regard, slot cooling fins, as described herein, may be usefulfor various winding architectures including, but not limited to, thewinding architectures as illustrated in FIG. 6A, FIG. 6B, and FIG. 6C.

Benefits, other advantages, and solutions to problems have beendescribed herein with regard to specific embodiments. Furthermore, theconnecting lines shown in the various figures contained herein areintended to represent exemplary functional relationships and/or physicalcouplings between the various elements. It should be noted that manyalternative or additional functional relationships or physicalconnections may be present in a practical system. However, the benefits,advantages, solutions to problems, and any elements that may cause anybenefit, advantage, or solution to occur or become more pronounced arenot to be construed as critical, required, or essential features orelements of the disclosure.

The scope of the disclosure is accordingly to be limited by nothingother than the appended claims, in which reference to an element in thesingular is not intended to mean “one and only one” unless explicitly sostated, but rather “one or more.” It is to be understood that unlessspecifically stated otherwise, references to “a,” “an,” and/or “the” mayinclude one or more than one and that reference to an item in thesingular may also include the item in the plural. All ranges and ratiolimits disclosed herein may be combined.

Moreover, where a phrase similar to “at least one of A, B, and C” isused in the claims, it is intended that the phrase be interpreted tomean that A alone may be present in an embodiment, B alone may bepresent in an embodiment, C alone may be present in an embodiment, orthat any combination of the elements A, B and C may be present in asingle embodiment; for example, A and B, A and C, B and C, or A and Band C. Different cross-hatching is used throughout the figures to denotedifferent parts but not necessarily to denote the same or differentmaterials.

The steps recited in any of the method or process descriptions may beexecuted in any order and are not necessarily limited to the orderpresented. Furthermore, any reference to singular includes pluralembodiments, and any reference to more than one component or step mayinclude a singular embodiment or step. Elements and steps in the figuresare illustrated for simplicity and clarity and have not necessarily beenrendered according to any particular sequence. For example, steps thatmay be performed concurrently or in different order are illustrated inthe figures to help to improve understanding of embodiments of thepresent disclosure.

Any reference to attached, fixed, connected or the like may includepermanent, removable, temporary, partial, full and/or any other possibleattachment option. Additionally, any reference to without contact (orsimilar phrases) may also include reduced contact or minimal contact.Surface shading lines may be used throughout the figures to denotedifferent parts or areas but not necessarily to denote the same ordifferent materials. In some cases, reference coordinates may bespecific to each figure.

Systems, methods and apparatus are provided herein. In the detaileddescription herein, references to “one embodiment,” “an embodiment,”“various embodiments,” etc., indicate that the embodiment described mayinclude a particular feature, structure, or characteristic, but everyembodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it may be within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed. After reading the description, it will be apparent to oneskilled in the relevant art(s) how to implement the disclosure inalternative embodiments.

Furthermore, no element, component, or method step in the presentdisclosure is intended to be dedicated to the public regardless ofwhether the element, component, or method step is explicitly recited inthe claims. No claim element is intended to invoke 35 U.S.C. 112(f)unless the element is expressly recited using the phrase “means for.” Asused herein, the terms “comprises,” “comprising,” or any other variationthereof, are intended to cover a non-exclusive inclusion, such that aprocess, method, article, or apparatus that comprises a list of elementsdoes not include only those elements but may include other elements notexpressly listed or inherent to such process, method, article, orapparatus.

What is claimed is:
 1. A method of manufacturing a stator for anelectric machine, the method comprising: manufacturing a slot coolingfin to extend into a slot defined between a first tooth, a second tooth,and a stator yoke; and disposing a coil into the slot; wherein the slotcooling fin extends into the coil.
 2. The method of claim 1, furthercomprising disposing the coil to surround the slot cooling fin.
 3. Themethod of claim 2, further comprising disposing the slot cooling fin toextend from at least one of the stator yoke or the first tooth.
 4. Themethod of claim 3, wherein the stator yoke defines a centrallongitudinal axis, a first surface facing radially outward, and a secondsurface facing radially inward.
 5. The method of claim 4, furthercomprising: disposing a first tooth tip to extend circumferentially froma radially inward end of the first tooth; disposing a second tooth tipto extend circumferentially from the radially inward end of the tooth,wherein the first tooth tip and the second tooth tip extend in oppositedirections from the first tooth; forming a first slot portion definedbetween the first tooth tip and the second surface; forming a secondslot portion defined between the second tooth tip and the secondsurface; and wherein the slot cooling fin extends into the first slotportion.
 6. The method of claim 4, further comprising disposing thestator yoke, the tooth, the first tooth, the second tooth, and the slotcooling fin to extend within a plane oriented orthogonal to the centrallongitudinal axis.
 7. The method of claim 4, wherein the slot coolingfin comprises a cantilever.
 8. The method of claim 4, wherein the slotcooling fin is disposed radially between the stator yoke and the firsttooth tip.
 9. The method of claim 4, further comprising disposing thetooth to extend radially from the second surface.
 10. The method ofclaim 4, wherein a first end of the slot cooling fin is coupled to atleast one of the tooth and the stator yoke and a second end of the slotcooling fin extends into the slot in a cantilevered manner.